Use of amphiphilic copolymers to stabilize dispersions of insoluble organic compounds for screening out UVradiation, dispersions stabilized with these copolymers and cosmetic compositions containing them

ABSTRACT

The invention relates to the use of at least one amphiphilic copolymer comprising at least one hydrophilic block and at least one hydrophobic block, to stabilize dispersions of insoluble organic compounds comprising at least one group that absorbs UV radiation, which is in the form of particles with a mean size of between 10 nm and 5 μm, and also to dispersions stabilized with these amphiphilic copolymers and to cosmetic compositions for topical application, in particular antisun compositions, containing them.

[0001] The present invention relates to the use of amphiphiliccopolymers to stabilize dispersions of insoluble organic compoundscomprising at least one group that absorbs UV radiation, which are inthe form of particles with a mean size of between 10 nm and 5 μm, to thedispersions obtained, stabilized with these copolymers, and to cosmeticcompositions containing them, and also to a process for preparing suchdispersions.

[0002] Many cosmetic compositions for photoprotecting the skin have beenproposed to date.

[0003] These antisun compositions are often in the form of an emulsionof oil-in-water or water-in-oil type, of gels or of anhydrous productscontaining one or more organic and/or mineral, insoluble and/or soluble,lipophilic and/or hydrophilic screening agents capable of selectivelyabsorbing harmful UV radiation. The efficacy of these screening agentsis characterized by their molar extinction coefficient ε. The nature andconcentration of the screening agents in the antisun compositions arechosen as a function of the desired protection factor and the desiredprotection profile. Depending on their lipophilic or hydrophilic nature,the screening agents may be distributed either in the fatty phase or inthe aqueous phase of the antisun composition.

[0004] A large number of organic screening agents commonly used bearsubstituents that make them soluble in various cosmetic media: chains of2-ethylhexyl type, for example, make screening agents soluble in oils,and ionized groups such as sulphonic acid give them a certain level ofsolubility in polar solvents and in particular in water.

[0005] However, it has been observed that the presence of substituentson the chromophore results in a reduction in the absorbing power, andthere is thus great interest in being able to use screening agentscontaining an unsubstituted chromophore in order to fully exploit theirabsorption properties.

[0006] However, the insolubility of these screening agents in mostcosmetic solvents makes them difficult to handle. It has moreover beenfound that, in order to be fully effective, they must be in the form ofvery fine particles fully dispersed in the cosmetic medium.

[0007] One of the solutions for obtaining a satisfactory dispersion ofparticles of screening agents in cosmetic compositions consists in firstproducing a concentrated predispersion that will then be introduced intothe cosmetic medium.

[0008] Such predispersions of micronized insoluble organic screeningagents may be prepared by grinding up a dispersion of coarse particlesin the presence of one or more suitable dispersants, to the desiredparticle size. These dispersants are generally compounds withinterfacial activity, which position themselves at the solid/liquidinterface, thus preventing the aggregation and sedimentation of theparticles.

[0009] International patent application WO 97/03643 and patentapplication EP 0 893 119 describe a process for grinding (micronizing)insoluble organic screening agents in the presence of a dispersantchosen from alkylpolyglucosides of formula C_(n)H_(2n+1)O(C₆H₁₀O₅)_(x)Hin which n is an integer between 8 and 16 and x is between 1.4 and 1.6.

[0010] International patent application WO 95/22959 discloses a processfor micronizing insoluble organic screening agents in the presence of agrinding adjuvant chosen from alkylated polyvinylpyrrolidones,copolymers of vinylpyrrolidone and of vinyl acetate, acylglutamates,copolymers of acrylic acid and of tert-octylpropenamide,ditolylethersulphonic acid/formaldehyde condensation products, Carbomer®products, a commercial mixture of fatty acid esters comprising anethoxylated tristyrylphenol and phospholipids.

[0011] The use of the above dispersants and grinding adjuvants tostabilize dispersions of micronized organic UV screening agentsnevertheless poses a certain number of problems. Specifically, althoughthese dispersants can produce stable concentrated predispersions, thedilution of the predispersions in the cosmetic medium during thepreparation of the antisun compositions is generally accompanied by anat least partial desorption of the dispersants and a destabilization ofthe final antisun cosmetic composition.

[0012] Attempts have been made to overcome this instability observed atthe time of dilution of the predispersions by increasing theconcentration of dispersants. However, it has been found that such anincrease in the concentration had the consequence of harming thepersistence of the insoluble organic screening agents on the skin or thehair, i.e. of promoting their removal on contact with water.

[0013] Consequently, the aim of the present invention is to finddispersants for stabilizing—at relatively low concentrations that do notharm the remanence of the screening agents—both concentrated dispersionsof micronized insoluble organic screening agents and the cosmeticcompositions obtained by diluting these concentrated dispersions in acosmetic medium.

[0014] The Applicant has found that one particular group of polymershaving the common characteristic of comprising at least one block ofhydrophilic monomers and at least one block of hydrophobic monomers,known as “amphiphilic copolymers”, makes it possible to satisfactorilystabilize concentrated dispersions and dilute dispersions of fineparticles of insoluble organic compounds that absorb UV radiation.

[0015] Consequently, one subject of the present invention is the use ofat least one amphiphilic copolymer comprising at least one hydrophilicblock and at least one hydrophobic block, to stabilize dispersions ofinsoluble organic compounds comprising at least one group that absorbsUV radiation, which is in the form of particles with a mean size ofbetween 10 nm and 5 μm.

[0016] A subject of the invention is also a process for preparing suchdispersions, which consists in subjecting particles of the said organiccompound, suspended in a liquid medium, to a step of particle sizereduction, until a mean particle size of between 10 nm and 5 μm isobtained, and in adding, before, during or after the step of particlesize reduction, at least one amphiphilic copolymer comprising at leastone hydrophilic block and at least one hydrophobic block.

[0017] A subject of the invention is also dispersions comprising, in aliquid medium, at least one insoluble organic compound comprising atleast one group that absorbs UV radiation, in the form of particles witha mean size of between 10 nm and 5 μm, and at least one dispersantchosen from a particular group of amphiphilic copolymers comprising atleast one hydrophilic block and at least one hydrophobic block, and alsocosmetic compositions for topical application, in particularcompositions for photoprotecting the skin and/or the hair, prepared bydiluting its dispersions in a cosmetically acceptable medium.

[0018] In contrast with the dispersions of micronized organic UVscreening agents, stabilized with the dispersants of the prior art (seeWO 97/03643 and WO 95/22959), the dispersions of the present inventionstabilized with the amphiphilic polymers described in greater detailhereinbelow remain entirely stable—i.e. no aggregation, flocculation orsedimentation of the particles is observed—when cosmetic compositionsare prepared from these dispersions by dilution in a cosmeticallyacceptable medium. The stabilizing effect, observed at the time ofdilution, is obtained for small amounts of dispersing polymers, i.e. ofthe order of a few milligrams per square metre of surface area ofparticles only, which not only reduces the costs of the startingmaterials for the compositions, but above all has the advantage of notimpairing the remanence of the insoluble UV screening agents on the skinand/or the hair.

[0019] The photoprotective cosmetic compositions containing particles ofinsoluble organic UV screening agents, stabilized with the amphiphilicpolymers described below, are moreover distinguished by an excellentphotoprotective power and satisfactory cosmetic properties.

[0020] In the present invention, the expression “amphiphilic copolymercomprising at least one hydrophilic block and at least one hydrophobicblock” means polymers comprising at least two types of monomer “block”,each of the blocks consisting of a succession of identical monomers. Theamphiphilic polymers of the present invention may have a linearstructure in which the various blocks are linked together, alternately(hydrophilic/hydrophobic), one after the other. This type of polymerincluding diblock, triblock or polyblock linear structures is generallyknown in the field of macromolecular chemistry as “block copolymers”.However, the Applicant also intends to include in the definition of theamphiphilic copolymers used in the present invention polymers having abranched structure, for example a structure in which blocks of a firsttype (hydrophobic or hydrophilic) are attached to a main chain forming asecond type of block (hydrophilic or hydrophobic). These polymers aregenerally known as “grafting copolymers” or “copolymers with a combstructure”.

[0021] All these copolymers are known in the art and may be preparedaccording to processes such as free-radical polymerization followed by astep of polymerization-grafting, anionic or cationic polymerization,polycondensation, or alternatively according to a recent technique knownas “controlled free-radical polymerization” described, inter alia, in“New Method of Polymer Synthesis”, Blackie Academic & Professional,London, 1995, volume 2, page 1, or in Trends Polym. Sci. 4, page 183(1996) by C. J. Hawker, and especially by atom-transfer free-radicalpolymerization described in JACS, 117, page 5614 (1995), byMatyjasezwski et al.

[0022] The amphiphilic copolymers comprising at least one hydrophilicblock and at least one hydrophobic block, used for the stabilization ofdispersions of particles of insoluble UV screening agents in a liquidmedium, are preferably nonionic polymers. Specifically, given that thepredispersions and the cosmetic compositions prepared therefromgenerally contain an aqueous phase, the presence of many charges on thedispersing polymer would excessively increase its solubility in thedispersing medium and would consequently promote the desorption at thetime of dilution with a cosmetically acceptable medium.

[0023] Examples of preferred amphiphilic copolymers that may bementioned as dispersants in the present invention include:

[0024] polyalkoxylated aliphatic alcohols of formula:

H_(2n+1)C_(n)(CH₂CH₂O)_(x)(CH₂CH(CH₃)O)_(y)(CH(CH₃)CH₂O)_(z)H

[0025] in which

[0026] n is an integer between 5 and 20 and preferably between 7 and 19,

[0027] x is an integer between 2 and 20 and preferably between 4 and 10,

[0028] y is an integer between 2 and 20 and preferably between 4 and 10,

[0029] the sum of y+z being an integer between 2 and 20 and preferablybetween 2 and 12.

[0030] These products are marketed under the name Synperonic®, series LFand A, and the name Atplus® by the company Uniquema.

[0031] triblock copolymers of ethylene oxide and of propylene oxide, offormula

HO(CH₂CH₂O)_(a)(CH₂CH(CH₃)O)_(b)(CH₂CH₂O)_(c)H

[0032] in which a represents an integer between 2 and 150, b representsan integer between 10 and 80 and c represents an integer between 2 and150; the hydrophilic/lipophilic balance of these polymers varies as afunction of the values of a, b and c.

[0033] products of condensation of block copolymers of ethylene oxideand of propylene oxide with ethylenediamine, corresponding to theformula:

[0034]  these products being marketed by the company Uniquema,

[0035] block copolymers of styrene and of ethylene oxide. This type ofpolymer is marketed, for example, under the name Tegomer® by the companyGoldschmidt.

[0036] polyalkoxylated fatty alcohol diurethane polymers of formula:

[0037] in which

[0038] n represents a number between 40 and 70, m represents a numberbetween 5 and 20, R represents a C₈₋₃₀ alkyl group and L represents agroup derived from isophorone diisocyanate or from hexamethylenediisocyanate. Examples of these products that may be mentioned includePPG-14 laureth-60 isophoryldicarbamate (INCI name) and PPG-14 palmeth-60hexyldicarbamate (INCI name), which are sold, respectively, under thenames Elfacos® T211 and Elfacos® T212 by the company Akzo.

[0039] polyethoxylated polyolefin succinates, and in particular thepolyethoxylated polyisobutylene succinate of formula

[0040] in which

[0041] PIB represents a polyisobutylene chain, n represents an integerbetween 2 and 15 and preferably between 7 and 10, and m represents aninteger between 2 and 15 and preferably between 2 and 6. These polymersmay be prepared by condensation of a polyolefin such as polyisobutylenewith succinic anhydride according to the reaction

[0042]  followed by a polyethoxylation of the polyolefin succinateobtained. This type of product is sold, for example, under the nameOS149480 by the company Lubrizol.

[0043] block terpolymers of (meth)acrylic acid, of a C₁₀₋₃₀ alkyl(meth)acrylate and of polyethylene glycol (meth)acrylate. Preferredpolymers of this family that may be mentioned include terpolymers ofacrylic acid, of a C₁₅ alkyl acrylate and of polyethylene glycolacrylate (28 EO), sold, for example, under the name Dapral® GE 202 bythe company Akzo.

[0044] The insoluble organic compounds comprising at least one groupthat absorbs UV radiation, used in the present invention, are known.

[0045] For the purposes of the present invention, the expression“insoluble organic compound” means an organic compound that has asolubility in water of less than 0.1% by weight and a solubility of lessthan 1% by weight in most organic solvents, for instance liquidparaffin, fatty alkylbenzoates and fatty acid triglycerides.

[0046] The insoluble organic compounds comprising at least one groupthat absorbs UV radiation may be chosen especially from insolubleorganic UV screening agents of oxalanilide, triazine, benzotriazole,vinylamide, cinnamide, benzazole, benzofuran, arylvinylidene ketone,acrylonitrile amide, acrylonitrile sulphonamide, acrylonitrile carbamateand phenylenebis-(benzoxazinone) type.

[0047] Among the insoluble UV screening agents of oxalanilide type thatmay be mentioned are those corresponding to the formula:

[0048] in which T₁, T₁′, T₂ and T₂′ each independently represent a C₁-C₈alkyl radical or a C₁-C₈ alkoxy radical. These compounds are describedin patent application WO 95/22959. Examples that may be mentionedinclude the commercial products Tinuvin® 315 and Tinuvin® 312 sold bythe company Ciba-Geigy and corresponding, respectively, to the formulae:

[0049] The insoluble screening agents of triazine type correspond to thefollowing general formula:

[0050] in which R₁, R₂ and R₃ each independently represent a phenyl,phenoxy or pyrrolo group that is unsubstituted, or each independentlybear one, two or three substituents chosen from —OH, C₁₋₁₈ alkyl, C₁₋₁₈alkoxy, carboxy(C₁₋₁₈ alkyl), C₅₋C₈ cycloalkyl,methylbenzylidenecamphor, —(CH═CR′)_(n)(CO)—OR₄ in which R′ represents ahydrogen atom, a cyano group or a group COOR₄, with R₄=C₁₋₁₈ alkyl orcinnamyl, and n is 0 or 1.

[0051] These compounds are described in WO 97/03643, GB 2 286 774, EP743 309, WO 98/22447, GB 2 319 523 and EP-A-0 790 243.

[0052] Mention will be made more particularly of the followingcompounds:

[0053] 2,4,6-tris(diethyl 4′-aminobenzalmalonate)-s-triazine,

[0054] 2,4,6-tris(diisopropyl 4′-aminobenzalmalonate)-s-triazine,

[0055] 2,4,6-tris(dimethyl 4′-aminobenzalmalonate)-s-triazine,

[0056] 2,4,6-tris(ethyl α-cyano-4-aminocinnamate)-s-triazine.

[0057] Among the UV screening agents of triazine type that may be usedfor the present invention, mention may also be made of insolubles-triazine derivatives bearing benzotriazole and/or benzothiazolegroups, such as those described in patent application WO 98/25922.

[0058] Among these compounds, mention may be made more particularly of2,4,6-tris[(3′-benzotriazol-2-yl-2′-hydroxy-5′-methyl)phenylamino]-s-triazineand 2, 4,6-tris[(3′-benzotriazol-2-yl-2′-hydroxy-5′-tert-octyl)-phenylamino]-s-triazine.

[0059] Among the insoluble organic UV screening agents of benzotriazoletype that may be mentioned are those of formula (III) below, described,for example, in International patent application WO 95/22959:

[0060] in which R₅ denotes a hydrogen atom or a C₁₋₁₈ alkyl radical, R₆and R₇, which may be identical or different, each independently denote aC₁₋₁₈ alkyl radical optionally substituted with a phenyl group.

[0061] Examples of compounds of formula (III) that may be mentionedinclude the commercial products Tinuvin® 328, 320, 234 and 350 from thecompany Ciba-Geigy, corresponding respectively to the followingformulae:

[0062] Among the insoluble organic UV screening agents of benzotriazoletype that may also be mentioned are the compounds described in patentsU.S. Pat. No. 5,687,521, U.S. Pat. No. 5,373,037 and U.S. Pat. No.5,362,881, and in particular among those[2,4′-dihydroxy-3-(2H-benzotriazol-2-yl)-5-(1,1,3,3-tetramethylbutyl)-2′-n-octoxy-5′-benzoyl]diphenylmethaneof formula:

[0063] sold under the name Mixxim® PB30 by the company FairmountChemical.

[0064] Other insoluble organic UV screening agents of benzotriazole typeare the methylenebis(hydroxyphenyl-benzotriazole) derivatives of thefollowing structure:

[0065] in which R₈ and R₉, which may be identical or different, eachrepresent a C₁₋₁₈ alkyl radical that may be substituted with one or moreradicals chosen from C₁₋₄ alkyl, C₅₋₁₂ cycloalkyl or aryl. Thesecompounds are known and are described in patent applications U.S. Pat.No. 5,237,071, U.S. Pat. No. 5,166,355, GB-A-2 303 549, DE 197 26 184and EP-A-893 119.

[0066] In formula (IV) defined above, the C₁₋₁₈ alkyl groups may belinear or branched and are, for example, methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, tert-butyl, tert-octyl, n-amyl, n-hexyl,n-heptyl, n-octyl, isooctyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl,tetradecyl, hexadecyl or octadecyl; the C₅₋₁₂ cycloalkyl groups are, forexample, cyclopentyl, cyclohexyl or cyclooctyl; the aryl groups are, forexample, phenyl or benzyl.

[0067] Among the compounds of formula (IV) that are more particularlypreferred are those corresponding to the formulae:

[0068] Compound (a)2,2′-methylenebis[6-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol)]is sold in pure form under the name Mixxim® BB/100 by the companyFairmount Chemical and in micronized form under the name Tinosorb® M byCiba Geigy.

[0069] Compound (c)2,2′-methylenebis[6-(2H-benzotriazol-2-yl)-4-(methyl)phenol)] is soldunder the name Mixxim® BB/200 by the company Fairmount Chemical.

[0070] Among the insoluble organic screening agents of the vinylamidetype that may be mentioned, for example, are the compounds of formula(V) that are described in patent application WO 95/22959:

T₃—(Y)_(r)—C(═O)—C(T₄)═C(T₅)—N(T₆)(T₇)  (V)

[0071] in which T₃ is a C₁₋₁₈ and preferably C₁₋₅ alkyl radical, or aphenyl group optionally substituted with one, two or three radicalschosen from OH, C₁₋₁₈ alkyl, C₁₋₈ alkoxy or —C(═O)—OT₈ in which T₈represents a C₁₋₁₈ alkyl group; T₄, T₅, T₆ and T₇ each independentlyrepresent a C₁₋₁₈ and preferably C₁₋₅ alkyl radical or a hydrogen atom;Y represents an —NH— group or an oxygen atom and r is 0 or 1.

[0072] Among these compounds that will be mentioned more particularlyare:

[0073] 4-octylamino-3-penten-2-one;

[0074] ethyl 3-octylamino-2-butenoate;

[0075] 3-octylamino-1-phenyl-2-buten-1-one

[0076] 3-dodecylamino-1-phenyl-2-buten-1-one.

[0077] Among the organic screening agents of cinnamide type that may bementioned are compounds such as those described in patent application WO95/22959 and corresponding to the following formula:

[0078] in which

[0079] R₁₀ represents a hydrogen atom or a C₁₋₄ alkyl group, preferablymethyl or ethyl,

[0080] R₁₁ represents a hydrogen atom or a C₁₋₄ alkyl group, preferablymethyl or ethyl,

[0081] R₁₂ represents a group —(CONH)_(s)-phenyl in which s is 0 or 1and the phenyl group may be substituted with one, two or three groupschosen from OH, C₁₋₁₈ alkyl, C₁₋₈ alkoxy or —C(═O)—OR₁₃ in which R₁₃ isa C₁₋₁₈ alkyl, and more preferably R₁₂ represents a phenyl,4-methoxyphenyl or phenylaminocarbonyl group.

[0082] Mention may also be made of the bis[α,β-disubstituted cinnamide]dimers described, for example, in patent U.S. Pat No. 5,888,481, ofstructure:

[0083] in which

[0084] Ar₁ and Ar₂, which may be identical or different, each representa phenyl radical, an aromatic heterocycle, a group containing a fusedphenyl nucleus or a group containing a fused aromatic heterocycle, andmay bear one or more identical or different substituents,

[0085] B and D, which are other than a hydrogen atom, each independentlyrepresent an organic radical,

[0086] A and C each independently represent an organic radical, and

[0087] E represents a divalent organic radical,

[0088] with the exclusion of the compounds for which Ar₁ and Ar₂ bothrepresent a phenyl group bearing a substituent —OR in which R representsa hydrogen atom or an organic radical, A and C both represent a cyanogroup, B and D both represent a C₁₋₃₅ alkyl or alkenyl group, and Erepresents a divalent organic radical,

[0089] and in particular the compound of structure:

[0090] Among the insoluble organic screening agents of the benzazoletype that may be mentioned are those corresponding to one of thefollowing formulae:

[0091] in which

[0092] each of the symbols Y independently represents an oxygen orsulphur atom or a group NR₁₅,

[0093] each of the symbols Z independently represents a nitrogen atom ora CH group,

[0094] each of the symbols R₁₄ independently represents an OH group, ahalogen atom, a linear or branched C₁₋₈ alkyl group optionallycontaining a silicon atom, or a linear or branched C₁₋₈ alkoxy group,

[0095] each of the numbers m is independently 0, 1 or 2,

[0096] n represents an integer between 1 and 4 inclusive,

[0097] p is equal to 0 or 1,

[0098] each of the numbers q is independently equal to 0 or 1,

[0099] each of the symbols R₁₅ independently represents a hydrogen atom,a benzyl group or a linear or branched C₁₋₈ alkyl group optionallycontaining a silicon atom,

[0100] A represents a radical of valency n chosen from those offormulae:

[0101] in which each of the symbols R₁₆ independently represents ahalogen atom or a linear or branched C₁₋₄ alkyl or alkoxy group, orhydroxyl,

[0102] R₁₇ represents a hydrogen atom or a linear or branched C₁₋₄ alkylgroup,

[0103] c=0-4, d=0-3, e=0 or 1 and f=0-2.

[0104] These compounds are especially described in patents DE 676 103and CH 350 763, patent U.S. Pat. No. 5,501,850, patent U.S. Pat. No.5,961,960, patent application EP 0 669 323, patent U.S. Pat. No.5,518,713, patent U.S. Pat. No. 2,463,264, the article from J. Am. Chem.Soc., 79, 5706-5708, 1957, the article published in J. Am. Chem. Soc.,82, 609-611, 1960, patent application EP 0 921 126 and patentapplication EP 0 712 855.

[0105] As examples of preferred compounds of formula (VIII) of the2-arylbenzazole family, mention may be made of2-benzoxazol-2-yl-4-methylphenol,2-(1H-benzimidazol-2-yl)-4-methoxyphenol or 2-benzothiazol-2-ylphenol,these compounds possibly being prepared, for example, according to theprocesses described in patent CH 350 763.

[0106] As examples of preferred compounds of formula (VIII) of thebenzimidazolylbenzazole family, mention will be made of2,2′-bis(benzimidazole), 5,5′,6,6′-tetramethyl-2,2′-bis(benzimidazole),5,5′-di-methyl-2,2′-bis(benzimidazole),6-methoxy-2,2′-bis(benz-imidazole),2-(1H-benzimidazol-2-yl)benzothiazole,2-(1H-benzimidazol-2-yl)benzoxazole andN,N′-dimethyl-2,2′-bis(benzimidazole), these compounds possibly beingprepared according to the procedures described in patents U.S. Pat. No.5,961,960 and U.S. Pat. No. 2,463,264.

[0107] As examples of preferred compounds of formula (VIII) of thephenylenebenzazole family, mention will be made of1,4-phenylenebis(2-benzoxazolyl), 1,4-phenylenebis(2-benzimidazolyl),1,3-phenylenebis(2-benzoxazolyl), 1,2-phenylenebis(2-benzoxazolyl),1,2-phenylenebis(benzimidazolyl),1,4-phenylenebis(N-2-ethylhexyl-2-benzimidazolyl) and1,4-phenylenebis(N-trimethylsilylmethyl-2-benzimidazolyl), thesecompounds possibly being prepared according to the procedures describedin patent U.S. Pat. No. 2,463,264 and in the publications J. Am. Chem.Soc., 82, 609 (1960) and J. Am. Chem. Soc., 79, 5706-5708 (1957).

[0108] As examples of preferred compounds of formula (VIII) of thebenzofuranylbenzoxazole family, mention will be made of2-(2-benzofuranyl)benzoxazole, 2-(benzofuranyl)-5-methylbenzoxazole and2-(3-methyl-2-benzofuranyl)benzoxazole, these compounds possibly beingprepared according to the procedures described in patent U.S. Pat. No.5,518,713.

[0109] Preferred compounds of formula (IX) that may be mentioned, forexample, include 2,6-diphenyl-1,7-dihydrobenzo[1,2-d;4,5-d′]diimidazole,corresponding to the formula

[0110] or 2,6-distyryl-1,7-dihydrobenzo[1,2-d;4,5-d′]diimidazole oralternatively2,6-di(p-tert-butylstyryl)-1,7-dihydro-benzo[1,2-d;4,5-d′]diimidazole,which may be prepared according to the processes described in patentapplication EP 0 669 323.

[0111] A preferred compound of formula (X) that may be mentioned is5,5′-bis[(2-phenyl)benzimidazole] of formula:

[0112] the preparation of which is described in J. Chim. Phys., 64, 1602(1967).

[0113] Among these insoluble organic compounds for screening out UVradiation, the ones most particularly preferred are2-(1H-benzimidazol-2-yl)benzoxazole, 6-methoxy-2,2′-bis(benzimidazole),2-(1H-benzimidazole-2-yl)benzothiazole,1,4-phenylenebis(2-benzoxazolyl), 1,4-phenylenebis(2-benzimidazolyl),1,3-phenylenebis-(2-benzoxazolyl), 1,2-phenylenebis(2-benzoxazolyl),1,2-phenylenebis(2-benzimidazolyl) and1,4-phenylene-bis(N-trimethylsilylmethyl-2-benzimidazolyl).

[0114] Another family of insoluble screening agents is that of thearylvinylene ketones chosen from those corresponding to one of thefollowing formulae (XI) and (XII):

[0115] in which:

[0116] n=1 or 2,

[0117] A, in formula (XI) when n=1 or in formula (XII), is an arylradical chosen from formulae (a) to (d) below, or in formula (XI) whenn=2, is a radical chosen from formulae (e) to (h) below:

[0118] in which:

[0119] each of the symbols R₄ independently represents an OH group, ahalogen atom, a linear or branched C₁₋₆ alkyl group optionallycontaining a silicon atom, a linear or branched C₁₋₆ alkoxy groupoptionally containing a silicon atom, a linear or branched C₁₋₅alkoxycarbonyl group, or a linear or branched C₁₋₆ alkylsulphonamidegroup optionally containing a silicon atom or an amino acid function,

[0120] p represents an integer between 0 and 4 inclusive,

[0121] q represents 0 or 1,

[0122] R₁ represents hydrogen or an OH group,

[0123] R₂ represents hydrogen, a linear or branched C₁₋₆ alkyl groupoptionally containing a silicon atom, a cyano group, a C₁₋₆alkylsulphonyl group or a phenylsulphonyl group,

[0124] R₃ represents a linear or branched C₁₋₆ alkyl group optionallycontaining a silicon atom or a phenyl group that can form a bicycle andoptionally substituted with one or two radicals R₄,

[0125] or R₂ and R₃ together form a monocyclic, bicyclic or tricyclicC₂₋₁₀ hydrocarbon-based residue, optionally interrupted with one or morenitrogen, sulphur and oxygen atoms and possibly containing anothercarbonyl, and optionally substituted with a linear or branched C₁-C₈alkylsulphonamide group, optionally containing a silicon atom or anamino acid function; on condition that when n=1, R₂ and R₃ do not form acamphor nucleus.

[0126] As examples of insoluble compounds of formula (XI) in which n=1,for screening out UV radiation, mention may be made of the followingfamilies:

[0127] Styryl ketone (Kao JP 04 134 042) such as1-(3,4-dimethoxyphenyl)-4,4-dimethylpent-1-en-3-one:

[0128] Benzylidene cineole (E. Mariani et al., 16th IFSCC Congress, NewYork (1990)) such as1,3,3-trimethyl-5-(4-methoxybenzylidene)-2-oxabicyclo[2.2.2]octan-6-one:

[0129] Benzylidene chromanone (Kao JP 04 134 043) such as3-(4-methoxybenzylidene)-2,3,4a,8a-tetrahydrochromen-4-one:

[0130] Benzylidene thiochromanone (Kao JP 04 134 043) such as3-(4-methoxybenzylidene)-2,3,4a,8a-tetrahydrochromen-4-thione:

[0131] Benzylidene quinuclidinone (Merck EP 0 576 974) such as4-methoxybenzylidene-l-azabicyclo-[2.2.2]octan-3-one:

[0132] Benzylidene cycloalkanone (Henkel FR 2 395 023) such as2-(4-methoxybenzylidene)cyclopentanone and2-(4-methoxybenzylidene)cyclohexanone:

[0133] Benzylidene hydantoin (Ajinomoto JP 01 158 090) such as5-(3,4-dimethoxybenzylidene)imidazolidine-2,4-dione:

[0134] Benzylidene indanone (Kao JP 04 134 043) such as2-(4-methoxybenzylidene)indan-1-one:

[0135] Benzylidene tetralone (Kao JP 04 134 043) such as2-(4-methoxybenzylidene)-3,4-dihydro-2H-naphthalen-1-one:

[0136] Benzylidene furanone (L'Oreal EP 0 390 683) such as4-(4-methoxybenzylidene)-2,2,5,5-tetramethyldihydrofuran-3-one:

[0137] Benzylidene benzofuranone (Kao JP 04 134 041) such as2-benzylidenebenzofuran-3-one:

[0138] Benzylidene indanedione such as2-(3,5-di-tert-butyl-4-hydroxybenzylidene)indan-1,3-dione:

[0139] Benzylidene benzothiofuranone (Kao JP 04 134 043) such as2-benzylidenebenzo-[b]thiophen-3-one:

[0140] Benzylidene barbituric such as5-(4-methoxybenzylidene)-1,3-dimethylpyrimidine-2,4,6-trione:

[0141] Benzylidene pyrazolone such as4-(4-methoxybenzylidene)-5-methyl-2-phenyl-2,4-dihydropyrazol-3-one:

[0142] Benzylidene imidazolone such as5-(4-methoxybenzylidene)-2-phenyl-3,5-dihydroimidazol-4-one:

[0143] Chalcone such as 1-(2-hydroxy-4-methoxyphenyl)-3-phenylpropenone:

[0144] Benzylidene one (screening tautomeric form of thedibenzoylmethanes; L'Oreal FR 2 506 156) such as3-hydroxy-1-(2-hydroxy-4-methoxyphenyl)-3-phenylpropenone:

[0145] As examples of insoluble compounds of formula (XI) in which n=2,for screening out UV radiation, mention may be made of the followingfamilies:

[0146] Phenylenebis(methylidene-nor-camphor) (Merck EP 0 693 471), suchas 1,4-phenylenebis{3-methylidenebicyclo[2.2.1]heptan-2-one}:

[0147] Phenylenebis(methylidenecamphor) (L'Oreal FR 2 528 420) such as1,4-phenylenebis{3-methylidene-1,7,7-trimethylbicyclo[2.2.1]-heptan-2-one}:

[0148] or1,3-phenylenebis{3-methylidene-1,7,7-trimethylbicyclo[2.2.1]heptan-2-one}:

[0149] Phenylenebis(methylidenecamphorsulphonamide) (L'Oreal FR 2 529887) such as ethyl or 2-ethylhexyl1,4-phenylenebis(3,3′-methylidenecamphor-10,10′-sulphonamide):

[0150] Phenylenebis(methylidenecineole) (E. Mariani et al, 16th IFSCCCongress, New York (1990)) such as1,4-phenylenebis{5-methylidene-3,3-dimethyl-2-oxabicyclo[2.2.2]octan-6-one}:

[0151] Phenylenebis(methylidene ketotricyclodecane) (Merck EP 0 694 521)such as 1,4-phenylenebis(octahydro-4,7-methano-6-inden-5-one):

[0152] Phenylenebis(alkylene ketone) (Kao JP 04 134 041) such as1,4-phenylenebis(4,4-dimethylpent-1-en-3-one):

[0153] Phenylenebis(methylidenefuranone) (L'Oreal FR 2 638 354) such as1,4-phenylenebis(4-methylidene-2,2,5,5-tetramethyldihydrofuran-3-one):

[0154] Phenylenebis(methylidene quinuclidinone) (Merck EP 0 714 880)such as 1,4-phenylenebis{2-methylidene-1-azabicyclo[2.2.2]octan-3-one}:

[0155] Examples of compounds of formula (XII) that may be mentionedinclude the following families:

[0156] bis(benzylidene)cycloalkanone such as2,5-dibenzylidenecyclopentanone:

[0157] gamma-pyrone (Kao JP 04 290 882) such as2,6-bis(3,4-dimethoxyphenyl)pyran-4-one:

[0158] Another family of insoluble screening agents that may be used inthe present invention are the acrylonitrile amide, sulphonamide andcarbamate derivatives corresponding to the following formula

[0159] in which

[0160] X₂ represents a divalent radical of formula

[0161] —(C═O)—R′₃—(C═O)—,

[0162] —SO₂—R″₃—SO₂— or —(C═O)—O—R″₃—O—(C═O)—,

[0163] Y represents a radical —(C═O)—R₄ or —SO₂R₅,

[0164] R₂ represents a linear or branched C₁₋₈ alkyl group,

[0165] n is 0, 1 or 2,

[0166] R′₃ represents a single bond or R″₃,

[0167] R″₃ represents a linear or branched C₁₋₃₀ divalent alkyleneradical or a linear or branched C₃₋₃₀ divalent alkenylene radical, whichmay bear one or more hydroxyl substituents and which may contain, in thecarbon-based chain, one or more hetero atoms chosen from oxygen,nitrogen and silicon atoms,

[0168] R₄ represents a radical —OR₆ or —NHR₆,

[0169] R₅ represents a linear or branched C₁₋₃₀ alkyl radical or aphenyl nucleus that may be substituted with C₁₋₄ alkyl or alkoxyradicals,

[0170] R₆ represents a linear or branched C₁₋₃₀ alkyl or C₃₋₃₀ alkenylradical, which may bear one or more hydroxyl substituents and which maycontain, in the carbon-based chain, one or more hetero atoms chosen fromoxygen, nitrogen and silicon atoms.

[0171] Although, in formula (XIII) above, only the isomers in which thecyano substituent is in the cis position relative to thepara-aminophenyl substituent are represented, this formula must beunderstood as also including the corresponding trans isomers for each ofthe two double bonds and, independently, the cyano and para-aminophenylsubstituents may be in a cis or trans configuration relative to eachother.

[0172] Another family of insoluble organic screening agents that may beused according to the present invention is formed by thephenylenebis(benzoxazinone) derivatives of formula

[0173] in which R represents a divalent aromatic residue chosen from theformulae (e) to (h) below:

[0174] in which:

[0175] each of the symbols R₄ independently represents an OH group, ahalogen atom, a linear or branched C₁₋₆ alkyl group optionallycontaining a silicon atom, a linear or branched C₁₋₆ alkoxy groupoptionally containing a silicon atom, a linear or branched C₁₋₅alkoxycarbonyl group, or a linear or branched C₁₋₆ alkylsulphonamidegroup optionally containing a silicon atom or an amino acid function,

[0176] p represents an integer between 0 and 4 inclusive,

[0177] q represents 0 or 1.

[0178] Examples of insoluble compounds of formula (XIV) for screeningout UV radiation that may be mentioned include the followingderivatives:

[0179] 2,2′-p-phenylenebis(3,1-benzoxazin-4-one), commercial productCyasorb® UV-3638 from the company Cytec,

[0180] 2,2′-(4,4′-biphenylene)bis(3,1-benzoxazin-4-one),2,2′-(2,6-naphthylene)bis(3,1-benzoxazin-4-one).

[0181] Another particular family of insoluble organic screening agentsis polyvalent metal salts (for example Ca²⁺, Zn²⁺, Mg²⁺, Ba²⁺, Al³⁺ orZr⁴⁺) of sulphonated or carboxylated organic screening agents, such aspolyvalent metal salts of sulphonated benzylidenecamphor derivativessuch as those described in patent application FR-A-2 639 347, polyvalentmetal salts of sulphonated benzimidazole derivatives such as thosedescribed in patent application EP-A-893 119, and polyvalent metal saltsof cinnamic acid derivatives such as those described in patentapplication JP-87 166 517.

[0182] Mention may also be made of complexes of metals or of ammonium orof substituted ammonium of UV-A and/or UV-B organic screening agentssuch as those described in patent applications WO 93/10753, WO 93/11095and WO 95/05150.

[0183] The dispersions of insoluble organic UV screening agents that itis proposed to stabilize using the amphiphilic copolymers describedabove are preferably aqueous dispersions, i.e. water constitutes all ormost of the liquid dispersion medium.

[0184] They preferably contain from 5% to 70% by weight and inparticular from 30% to 50% by weight of particles of insoluble organiccompound comprising at least one group that absorbs UV radiation.

[0185] As mentioned above, the mean particle size of the insolubleorganic compound comprising at least one group that absorbs UV radiationis between 10 nm and 5 μm.

[0186] The mean particle size of the insoluble organic compoundcomprising at least one group that absorbs UV radiation is preferablybetween 10 nm and 2 μm, in particular between 20 nm and 1.5 μm andideally between 30 nm and 1.0 μm.

[0187] In general, the mean particle size will correspond to thenumber-average diameter distribution.

[0188] The mean particle size may be determined by any standard methodsuch as optical methods (quasielastic scattering or laser scattering),centrifugation methods or methods of microscopic visualization and imageanalysis.

[0189] The amount of amphiphilic copolymer required to obtainsatisfactory stability and persistence properties depends, inter alia,on the nature of the amphiphilic copolymer and on the nature,concentration, size and specific surface area of the particles of theinsoluble organic UV screening agents to be stabilized.

[0190] It has been found that it is possible to satisfactorily stabilizethe dispersions of insoluble organic UV screening agents of the presentinvention by using an amount of amphiphilic copolymer comprising atleast one hydrophilic block and at least one hydrophobic block ofbetween 1 and 10 mg/m² and preferably between 1 and 5 mg/m², of surfacearea of particles of insoluble organic compound comprising at least onegroup that absorbs UV radiation.

[0191] A subject of the present invention is also a process forpreparing dispersions of insoluble organic compounds comprising at leastone group that absorbs UV radiation. This process consists in subjectingparticles of the said organic compound, suspended in a liquid medium, toa step of particle size reduction until a mean size of between 10 nm and5 μm is obtained, and in adding, before, during or after the step ofsize reduction, at least one amphiphilic copolymer comprising at leastone hydrophilic block and at least one hydrophobic block such as thosedescribed above.

[0192] The step of particle size reduction in the process formanufacturing dispersions of the present invention may be carried out byany suitable means, such as dry grinding or grinding in a solventmedium, screening, atomization, micronization, spraying or any chemicalprocess such as precipitation by emulsion or dilution.

[0193] According to one preferred embodiment of the process of thepresent invention, the step of particle size reduction is a grindingoperation in an aqueous medium.

[0194] Although it is possible to add the amphiphilic copolymer aloneafter the grinding step, one preferred embodiment comprises the additionof the amphiphilic copolymer before grinding in the premix, i.e. in thesuspension of coarse particles in a liquid medium, or alternativelyduring the grinding step.

[0195] One example of a process for reducing the size of the particlesby grinding insoluble organic screening agents is described in documentsWO 95/22959 and WO 97/03643.

[0196] The grinding apparatus used according to these documents may be ajet mill, a ball mill, a vibration mill or a hammer mill and preferablya high-spin-speed mill or an impact mill and more particularly a rotaryball mill, a vibrating mill, a tube mill or a rod mill.

[0197] A subject of the invention is also dispersions of particles ofinsoluble organic compounds comprising at least one group that absorbsUV radiation, prepared according to the process described above,containing a dispersant chosen from a particular group of amphiphiliccopolymers comprising at least one hydrophilic block and at least onehydrophobic block, and also cosmetic compositions for topicalapplication, in particular compositions intended for photoprotecting theskin and/or the hair, prepared by dilution of its dispersions in acosmetically acceptable medium.

[0198] The particular group of amphiphilic copolymers includes:

[0199] polyalkoxylated aliphatic alcohols of formula:

H_(2n+1)C_(n)(CH₂CH₂O)_(x)(CH₂CH(CH₃)O)_(y)(CH(CH₃)CH₂O)_(z)H

[0200] in which

[0201] n is an integer between 5 and 20 and preferably between 7 and 19,

[0202] x is an integer between 2 and 20 and preferably between 4 and 10,

[0203] y is an integer between 2 and 20 and preferably between 4 and 10,

[0204] the sum of y+z being an integer between 2 and 20 and preferablybetween 2 and 20.

[0205] triblock copolymers of ethylene oxide and of propylene oxide, offormula

HO(CH₂CH₂O)_(a)(CH₂CH(CH₃)O)_(b)(CH₂CH₂O)_(c)H

[0206] in which a represents an integer between 2 and 150, b representsan integer between 10 and 80 and c represents an integer between 2 and150;

[0207] the products of condensation of block copolymers of ethyleneoxide and of propylene oxide with ethylenediamine, corresponding to theformula:

[0208] block copolymers of styrene and of ethylene oxide,

[0209] polyalkoxylated polyolefin succinates, and in particular thepolyethoxylated polyisobutylene succinate of formula

[0210] in which

[0211] PIB represents a polyisobutylene chain, n represents an integerbetween 2 and 15 and preferably between 7 and 10, and m represents aninteger between 2 and 15, preferably between 2 and 6;

[0212] block terpolymers of (meth)acrylic acid, of a C₁₀₋₃₀ alkyl(meth)acrylate and of polyethylene glycol (meth)acrylate.

[0213] The insoluble organic compounds comprising at least one groupthat absorbs UV radiation, the mean particle size of these screeningagents and also the amount of amphiphilic copolymer used to stabilizethem are the same as those specified above.

[0214] The cosmetic compositions of the present invention, obtained bydilution in a cosmetically acceptable medium, preferably contain from0.1% to 15% by weight and in particular from 0.2% to 10% by weight ofparticles of insoluble organic compound comprising at least one groupthat absorbs UV radiation.

[0215] The cosmetic compositions of the present invention may alsocontain one or more water-soluble or liposoluble organic sunscreens thatare active in the UV-A and/or UV-B range.

[0216] These water-soluble or liposoluble sunscreens may be chosenespecially from cinnamic derivatives, dibenzoylmethane derivatives,salicylic derivatives, benzylidenecamphor derivatives, soluble triazinederivatives such as those described in patents or patent applicationsU.S. Pat. No. 4,367,390, EP 0 863 145, EP 0 517 104, EP 0 570 838, EP 0796 851, EP 0 775 698, EP 0 878 469, EP 0 933 376, EP 0 507 691, EP 0507 692, EP 0 790 243, EP 0 944 624 and U.S. Pat. No. 4,724,137;benzophenone derivatives; β,β′-diphenyl acrylate derivatives;phenylbenzimidazole derivatives; anthranilic derivatives; imidazolinederivatives; p-aminobenzoic acid derivatives; screeninghydrocarbon-based polymers and screening silicones such as thosedescribed especially in patent application WO 93/04665; dimers derivedfrom α-alkylstyrene as described in patent application DE 198 55 649;and also mixtures of these screening agents.

[0217] As examples of such additional water-soluble or liposolublesunscreens that are active in the UV-A and/or UV-B range, mention may bemade of the following compounds, denoted by their INCI name, and alsomixtures thereof:

[0218] para-Aminobenzoic Acid Derivatives:

[0219] PABA,

[0220] Ethyl PABA,

[0221] Ethyl dihydroxypropyl PABA,

[0222] Ethylhexyl dimethyl PABA sold in particular under the trade name“Escalol 507” by ISP,

[0223] Glyceryl PABA,

[0224] PEG-25 PABA sold under the trade name “Uvinul P25” by BASF,

[0225] Salicylic Derivatives:

[0226] Homosalate sold under the trade name “Eusolex HMS” by Rona/EMIndustries,

[0227] Ethylhexyl salicylate sold under the trade name “Neo Heliopan OS”by Haarmann and Reimer,

[0228] Dipropylene glycol salicylate sold under the trade name “Dipsal”by Scher,

[0229] TEA salicylate sold under the trade name “Neo Heliopan TS” byHaarmann and Reimer,

[0230] Dibenzoylmethane Derivatives:

[0231] Butyl methoxydibenzoylmethane sold in particular under the tradename “Parsol 1789” by Hoffmann LaRoche,

[0232] Isopropyldibenzoylmethane,

[0233] Cinnamic Derivatives:

[0234] Ethylhexyl methoxycinnamate sold in particular under the tradename “Parsol MCX” by Hoffmann LaRoche,

[0235] Isopropyl methoxycinnamate,

[0236] Isoamyl methoxycinnamate sold under the trade name “Neo HeliopanE 1000” by Haarmann and Reimer,

[0237] Cinoxate,

[0238] DEA methoxycinnamate,

[0239] Diisopropyl methylcinnamate,

[0240] Glyceryl ethylhexanoate dimethoxycinnamate,

[0241] β,β′-diphenylacrylate Derivatives:

[0242] Octocrylene sold in particular under the trade name “Uvinul-539”by BASF,

[0243] Benzophenone Derivatives:

[0244] Benzophenone-1 sold under the trade name “Uvinul 400” by BASF,

[0245] Benzophenone-2 sold under the trade name “Uvinul D50” by BASF,

[0246] Benzophenone-3 or Oxybenzone, sold under the trade name “UvinulM-40” by BASF,

[0247] Benzophenone-4 sold under the trade name “Uvinul MS-40” by BASF,

[0248] Benzophenone-5,

[0249] Benzophenone-6 sold under the trade name “Helisorb 11” byNorquay,

[0250] Benzophenone-8 sold under the trade name “Spectra-Sorb UV-24” byAmerican Cyanamid,

[0251] Benzophenone-9 sold under the trade name “Uvinul DS-49” by BASF,

[0252] Benzophenone-12,

[0253] Benzylidenecamphor Derivatives:

[0254] Benzylidenecamphorsulphonic acid manufactured under the name“Mexoryl SL” by Chimex,

[0255] Camphor benzalkonium methosulphate manufactured under the name“Mexoryl SO” by Chimex,

[0256] Terephthalylidenedicamphorsulphonic acid manufactured under thename “Mexoryl SX” by Chimex,

[0257] Polyacrylamidomethylbenzylidenecamphor manufactured under thename “Mexoryl SW” by Chimex,

[0258] Phenylbenzimidazole Derivatives:

[0259] Phenylbenzimidazolesulphonic acid sold in particular under thetrade name “Eusolex 232” by Merck,

[0260] Benzimidazilate sold under the trade name “Neo Heliopan AP” byHaarmann and Reimer,

[0261] Triazine Derivatives:

[0262] Anisotriazine sold under the trade name “Tinosorb S” byCiba-Geigy,

[0263] Ethylhexyltriazone sold in particular under the trade name“Uvinul T150” by BASF,

[0264] Diethylhexylbutamidotriazone sold under the trade name “UvasorbHEB” by Sigma 3V,

[0265] Phenylbenzotriazole Derivatives:

[0266] Drometrizole trisiloxane sold under the trade name “Silatrizole”by Rhodia Chimie,

[0267] Anthranilic Derivatives:

[0268] a) Menthyl anthranilate sold under the trade name “Neo HeliopanMA” by Haarmann and Reimer,

[0269] Imidazoline Derivatives:

[0270] b) Ethylhexyldimethoxybenzylidenedioxoimidazoline propionate,

[0271] Benzalmalonate Derivatives:

[0272] c) Polyorganosiloxane containing benzalmalonate functions, soldunder the trade name “Parsol SLX” by Hoffmann LaRoche.

[0273] The water-soluble or liposoluble organic UV screening agents thatare more particularly preferred are chosen from the following compounds:

[0274] Ethylhexyl salicylate,

[0275] Butyl methoxydibenzoylmethane,

[0276] Ethylhexyl methoxycinnamate,

[0277] Octocrylene,

[0278] Phenylbenzimidazolesulphonic acid,

[0279] Terephthalylidenedicamphorsulphonic acid,

[0280] Benzophenone-3,

[0281] Benzophenone-4,

[0282] Benzophenone-5,

[0283] Benzimidazilate,

[0284] Anisotriazine,

[0285] Ethylhexyltriazone,

[0286] Diethylhexylbutamidotriazone,

[0287] Drometrizole trisiloxane,

[0288] and mixtures thereof.

[0289] The cosmetic compositions according to the invention may alsocontain agents for artificially tanning and/or browning the skin(self-tanning agents) such as dihydroxyacetone (DHA).

[0290] The cosmetic compositions according to the invention may alsocontain one or more mineral pigments and in particular metal oxidenanopigments, that may be coated or uncoated, such as, for example,nanopigments of titanium oxide in amorphous or crystalline (rutileand/or anatase) form, of iron oxide, of zinc oxide, of zirconium oxideor of cerium oxide. These nanopigments have a mean particle size ofbetween 5 nm and 100 nm and preferably between 10 nm and 50 nm, and areall known UV-photoprotective agents.

[0291] These nanopigments may be coated with known coating agents suchas, for example, alumina and/or aluminium stearate.

[0292] Such coated or uncoated nanopigments are described, for example,in patent applications EP-A-0 518 772 and EP-A-0 518 773.

[0293] The cosmetic compositions may also contain common formulationadjuvants such as fatty substances, physiologically acceptable organicsolvents, silicones, surfactants, anionic, cationic, nonionic oramphoteric polymers or mixtures thereof, thickeners, antioxidants,opacifiers, stabilizers, antifoams, fragrances, preserving agents,fillers, sequestering agents, propellants, pH modifiers and colorants,and mixtures thereof.

[0294] They may also contain one or more cosmetic active principleschosen, for example, from softeners, hydroxy acids, vitamins,moisturizers, emollients, free-radical scavengers, substance Pantagonists and anti-inflammatory agents, and mixtures of thesecompounds.

[0295] The fatty substances may consist of an oil or a wax or mixturesthereof, and they also comprise fatty acids, fatty alcohols and fattyacid esters. The oils may be chosen from animal, plant, mineral andsynthetic oils and especially from liquid petroleum jelly, liquidparaffin, silicone oils, that may be volatile or non-volatile,isoparaffins, polyolefins, fluoro oils and perfluoro oils. Similarly,the waxes may be chosen from animal, fossil, plant, mineral andsynthetic waxes that are known per se.

[0296] Among the organic solvents that may be mentioned are loweralcohols and polyols such as ethanol, isopropanol, propylene glycol,glycerol and sorbitol.

[0297] The thickeners may be chosen especially from guar gums andcelluloses, that may be modified or unmodified, such as hydroxypropylguar gum, methylhydroxyethylcellulose, hydroxypropylmethylcellulose orhydroxyethylcellulose.

[0298] Needless to say, the person skilled in the art will take care toselect this or these optional additional compound(s) and/or the amountsthereof such that the advantageous properties intrinsic to theinvention, and in particular the stability of the dispersions, are notadversely affected by the envisaged addition(s).

[0299] The compositions of the invention may be prepared according totechniques that are well known to those skilled in the art, inparticular those intended for preparing emulsions of oil-in-water orwater-in-oil type.

[0300] This composition may be in particular in the form of a simple orcomplex emulsion (O/W, W/O, O/W/O or W/O/W emulsion) such as a cream, amilk, a gel or a cream-gel, and may optionally be packaged as an aerosoland be in the form of a mousse or a spray.

[0301] When it is an emulsion, the aqueous phase of this emulsion maycomprise a nonionic vesicular dispersion prepared according to knownprocesses (Bangham, Standish and Watkins, J. Mol. Biol. 13, 238 (1965),FR 2 315 991 and FR 2 416 008).

[0302] The cosmetic composition of the invention may be used as acomposition for protecting the human epidermis or the hair againstultraviolet rays, as an antisun composition or as a makeup product.

[0303] When the cosmetic composition according to the invention is usedfor protecting the human epidermis against UV rays, or as an antisuncomposition, it may be in the form of a suspension or a dispersion insolvents or fatty substances, in the form of a nonionic vesiculardispersion or in the form of an emulsion, preferably of oil-in-watertype, such as a cream or a milk, or in the form of an ointment, a gel, acream-gel, an aerosol mousse or a spray.

[0304] When the cosmetic composition according to the invention is usedfor protecting the hair against UV rays, it may be in the form of ashampoo, a lotion, a gel, an emulsion or a nonionic vesicular dispersionand may constitute, for example, a rinse-out composition, to be appliedbefore or after shampooing, before or after dyeing or bleaching, before,during or after permanent-waving or straightening the hair, a styling ortreating lotion or gel, a blow-drying or hairsetting lotion or gel, or acomposition for permanent-waving, straightening, dyeing or bleaching thehair.

[0305] When the composition is used as a makeup product for theeyelashes, the eyebrows or the skin, such as an epidermal treatmentcream, a foundation, a tube of lipstick, an eyeshadow, a face powder, amascara or an eyeliner, it may be in aqueous form, for instanceoil-in-water or water-in-oil emulsions, nonionic vesicular dispersionsor suspensions.

[0306] As a guide, for the antisun formulations in accordance with theinvention, which contain a support of oil-in-water emulsion type, theaqueous phase generally represents from 50% to 95% by weight andpreferably from 70% to 90% by weight, relative to the total formulation,the oily phase represents from 5% to 50% by weight and preferably from10% to 30% by weight, relative to the total formulation, and the(co)emulsifier(s) represent(s) from 0.5% to 20% by weight and preferablyfrom 2% to 10% by weight, relative to the total formulation.

1. Use of an amphiphilic copolymer comprising at least one hydrophilicblock and at least one hydrophobic block, to stabilize dispersions ofinsoluble organic compounds comprising at least one group that absorbsUV radiation, which is in the form of particles with a mean size ofbetween 10 nm and 5 μm.
 2. Use according to claim 1, characterized inthat the dispersions of insoluble organic compounds comprising at leastone group that absorbs UV radiation are aqueous dispersions.
 3. Useaccording to claim 1 or 2, characterized in that the amphiphiliccopolymer comprising at least one hydrophilic block and at least onehydrophobic block is a nonionic polymer.
 4. Use according to claim 3,characterized in that the amphiphilic copolymer comprising at least onehydrophilic block and at least one hydrophobic block is chosen from thegroup formed by polyalkoxylated aliphatic alcohols of formula:H_(2n+1)C_(n)(CH₂CH₂O)_(x)(CH₂CH(CH₃)O)_(y)(CH(CH₃)CH₂O)_(z)H in which nis an integer between 5 and 20 and preferably between 7 and 19, x is aninteger between 2 and 20 and preferably between 4 and 10, y is aninteger between 2 and 20 and preferably between 4 and 10, the sum of y+zbeing an-integer between 2 and 20 and preferably between 2 and 12;triblock copolymers of ethylene oxide and of propylene oxide, of formulaHO(CH₂CH₂O)_(a)(CH₂CH(CH₃)O)_(b)(CH₂CH₂O)_(c)H in which a represents aninteger between 2 and 150, b represents an integer between 10 and 80 andc represents an integer between 2 and 150; products of condensation ofblock copolymers of ethylene oxide and of propylene oxide withethylenediamine, corresponding to the formula:

block copolymers of styrene and of ethylene oxide, polyalkoxylated fattyalcohol diurethane polymers of formula:

in which n represents a number between 40 and 70, m represents a numberbetween 5 and 20, R represents a C₈₋₃₀ alkyl group and L represents agroup derived from isophorone diisocyanate or from hexamethylenediisocyanate, polyethoxylated polyolefin succinates, and in particularthe polyethoxylated polyisobutylene succinate of formula

in which PIB represents a polyisobutylene chain, n represents an integerbetween 2 and 15 and preferably between 7 and 10, and m represents aninteger between 2 and 15 and preferably between 2 and 6; blockterpolymers of (meth)acrylic acid, of a C₁₀₋₃₀ alkyl (meth)acrylate andof polyethylene glycol (meth)acrylate.
 5. Use according to any one ofthe preceding claims, characterized in that the insoluble organiccompounds comprising at least one group that absorbs UV radiation arechosen from insoluble UV screening agents of oxalanilide, triazine,benzotriazole, vinylamide, cinnamide, benzazole, benzofuran,arylvinylidene ketone, acrylonitrile amide, acrylonitrile sulphonamide,acrylonitrile carbamate and phenylenebis(benzoxazinone) type.
 6. Useaccording to claim 5, characterized in that the insoluble UV screeningagents of oxalanilide type are chosen from those of formula

in which T₁, T₁′, T₂ and T₂′ each independently represent a C₁₋₈ alkylradical or a C₁₋₈ alkoxy radical.
 7. Use according to claim 5,characterized in that the insoluble UV screening agents of triazine typeare chosen from those of formula

in which R₁, R₂ and R₃ each independently represent a phenyl, phenoxy orpyrrolo group that is unsubstituted, or each independently bear one, twoor three substituents chosen from —OH, C₁₋₁₈ alkyl, C₁₋₁₈ alkoxy,carboxy(C₁₋₁₈ alkyl), C₅-C₈ cycloalkyl, methylbenzylidenecamphor,—(CH═CR′)_(n)(CO)—OR₄ in which R′ represents a hydrogen atom, a cyanogroup or a group COOR₄, with R₄=C₁₋₁₈ alkyl or cinnamyl, and n is 0or
 1. 8. Use according to claim 5, characterized in that the insolubleUV screening agents of benzotriazole type are chosen from those offormula

in which R₅ denotes a hydrogen atom or a C₁₋₁₈ alkyl radical, R₆ and R₇,which may be identical or different, denote a C₁₋₁₈ alkyl radicaloptionally substituted with a phenyl group, or of formula

in which R₈ and R₉, which may be identical or different, each representa C₁₋₁₈ alkyl radical that may be substituted with one or more radicalschosen from C₁₋₄ alkyl, C₅₋₁₂ cycloalkyl or aryl.
 9. Use according toclaim 5, characterized in that the insoluble UV screening agents ofvinylamide type are chosen from those of formulaT₃—(Y)_(r)—C(═O)—C(T₄)═C(T₅)—N(T₆)(T₇)  (V) in which T₃ is a C₁₋₁₈ andpreferably C₁₋₅ alkyl radical, or a phenyl group optionally substitutedwith one, two or three radicals chosen from OH, C₁₋₁₈ alkyl, C₁₋₈ alkoxyor —C(═O)—OT₈ in which T₈ represents a C₁₋₁₈ alkyl group; T₄, T₅, T₆ andT₇ each independently represent a C₁₋₁₈ and preferably C₁₋₅ alkylradical or a hydrogen atom; Y represents —NH— or an oxygen atom and r is0 or
 1. 10. Use according to claim 5, characterized in that theinsoluble UV screening agents of cinnamide type are chosen from those offormula

in which R₁₀ represents a hydrogen atom or a C₁₋₄ alkyl group, R₁₁represents a hydrogen atom or a C₁₋₄ alkyl group, R₁₂ represents a group—(CONH)_(s)-phenyl in which s is 0 or 1 and the phenyl group may besubstituted with one, two or three groups chosen from OH, C₁₋₁₈ alkyl,C₁₋₈ alkoxy or —C(═O)—OR₁₃ in which R₁₃ is a C₁₋₁₈ alkyl, and morepreferably R₁₂ represents a phenyl, 4-methoxyphenyl orphenylaminocarbonyl group.
 11. Use according to claim 5, characterizedin that the insoluble screening agents of cinnamide type arebis(α,β-disubstituted cinnamides) chosen from those of formula:

in which Ar₁ and Ar₂, which may be identical or different, eachrepresent a phenyl radical, an aromatic heterocycle, a group containinga fused phenyl nucleus or a group containing a fused aromaticheterocycle, and may bear one or more identical or differentsubstituents, B and D, which are other than a hydrogen atom, eachindependently represent an organic radical, A and C each independentlyrepresent an organic radical, and E represents a divalent organicradical, with the exclusion of the compounds for which Ar₁ and Ar₂ bothrepresent a phenyl group bearing a substituent —OR in which R representsa hydrogen atom or an organic radical, A and C both represent a cyanogroup, B and D both represent a C₁₋₃₅ alkyl or alkenyl group, and Erepresents a divalent organic radical.
 12. Use according to claim 5,characterized in that the insoluble UV screening agents of benzazole orbenzofuran type are chosen from those of formula:

in which each of the symbols Y independently represents an oxygen orsulphur atom or a group NR₁₅, each of the symbols Z independentlyrepresents a nitrogen atom or a CH group, each of the symbols R₁₄independently represents an OH group, a halogen atom, a linear orbranched C₁₋₈ alkyl group optionally containing a silicon atom, or alinear or branched C₁₋₈ alkoxy group, each of the numbers m isindependently 0, 1 or 2, n represents an integer between 1 and 4inclusive, p is equal to 0 or 1, each of the numbers q is independentlyequal to 0 or 1, each of the symbols R₁₅ independently represents ahydrogen atom, a benzyl group or a linear or branched C₁₋₈ alkyl groupoptionally containing a silicon atom, A represents a radical of valencyn chosen from those of formulae:

in which each of the symbols R₁₆ independently represents a halogen atomor a linear or branched C₁₋₄ alkyl or alkoxy group, or hydroxyl, R₁₇represents a hydrogen atom or a linear or branched C₁₋₄ alkyl group,c=0-4, d=0-3, e=0 or 1 and f=0-2.
 13. Use according to claim 5,characterized in that the insoluble screening agents of arylvinyleneketone type are chosen from those of formulae:

in which: n=1 or 2, A, in formula (XI) when n=1 or in formula (XII), isan aryl radical chosen from formulae (a) to (d) below, or in formula(XI) when n=2, is a radical chosen from formulae (e) to (h) below:

in which: each of the symbols R₄ independently represents an OH group, ahalogen atom, a linear or branched C₁₋₆ alkyl group optionallycontaining a silicon atom, a linear or branched C₁₋₆ alkoxy groupoptionally containing a silicon atom, a linear or branched C₁₋₅alkoxycarbonyl group, or a linear or branched C₁₋₆ alkylsulphonamidegroup optionally containing a silicon atom or an amino acid function, prepresents an integer between 0 and 4 inclusive, q represents 0 or 1, R₁represents hydrogen or an OH group, R₂ represents hydrogen, a linear orbranched C₁₋₆ alkyl group optionally containing a silicon atom, a cyanogroup, a C₁₋₆ alkylsulphonyl group or a phenylsulphonyl group, R₃represents a linear or branched C₁₋₆ alkyl group optionally containing asilicon atom or a phenyl group that can form a bicycle and optionallysubstituted with one or two radicals R₄, or R₂ and R₃ together form amonocyclic, bicyclic or tricyclic C₂₋₁₀ hydrocarbon-based residue,optionally interrupted with one or more nitrogen, sulphur and oxygenatoms and possibly containing another carbonyl, and optionallysubstituted with a linear or branched C₁-C₈ alkylsulphonamide group,optionally containing a silicon atom or an amino acid function; oncondition that when n=1, R₂ and R₃ do not form a camphor nucleus. 14.Use according to claim 5, characterized in that the insoluble screeningagents of acrylonitrile amide, acrylonitrile sulphonamide andacrylonitrile carbamate type are chosen from those of formula:

in which X₂ represents a divalent radical of formula —(C═O)—R′₃—(C═O)—,—SO₂—R″₃—SO₂— or —(C═O)—O—R″₃—O—(C═O)—, Y represents a radical —(C═O)—R₄or —SO₂R₅, R₂ represents a linear or branched C₁₋₈ alkyl group, n is 0,1 or 2, R′₃ represents a single bond or R″₃, R″₃ represents a linear orbranched C₁₋₃₀ divalent alkylene radical or a linear or branched C₃₋₃₀divalent alkenylene radical, which may bear one or more hydroxylsubstituents and which may contain, in the carbon-based chain, one ormore hetero atoms chosen from oxygen, nitrogen and silicon atoms, R₄represents a radical —OR₆ or —NHR₆, R₅ represents a linear or branchedC₁₋₃₀ alkyl radical or a phenyl nucleus that may be substituted withC₁₋₄ alkyl or alkoxy radicals, R₆ represents a linear or branched C₁₋₃₀alkyl or C₃₋₃₀ alkenyl radical, which may bear one or more hydroxylsubstituents and which may contain, in the carbon-based chain, one ormore hetero atoms chosen from oxygen, nitrogen and silicon atoms. 15.Use according to claim 5, characterized in that the insoluble organicscreening agents of phenylenebis(benzoxazinone) type are chosen fromthose of formula:

in which R represents a divalent aromatic residue chosen from theformulae (e) to (h) below:

in which: each of the symbols R₄ independently represents an OH group, ahalogen atom, a linear or branched C₁₋₆ alkyl group optionallycontaining a silicon atom, a linear or branched C₁₋₆ alkoxy groupoptionally containing a silicon atom, a linear or branched C₁₋₅alkoxycarbonyl group, or a linear or branched C₁₋₆ alkylsulphonamidegroup optionally containing a silicon atom or an amino acid function, prepresents an integer between 0 and 4 inclusive, q represents 0 or 1.16. Use according to any one of the preceding claims, characterized inthat the mean particle size of the insoluble organic compound comprisingat least one group that absorbs UV radiation is between 10 nm and 2 μm,preferably between 20 nm and 1.5 μm and in particular between 30 nm and1.0 μm.
 17. Use according to any one of the preceding claims,characterized in that the dispersion contains from 5% to 70% andpreferably from 30% to 50% by weight of particles of insoluble organiccompound comprising at least one group that absorbs UV radiation. 18.Use according to any one of the preceding claims, characterized in thatthe amphiphilic copolymer comprising at least one hydrophilic block andat least one hydrophobic block is used in a proportion of from 1 to 10mg/m² and preferably in a proportion of from 1 to 5 mg/m² of surfacearea of particles of insoluble organic compound comprising at least onegroup that absorbs UV radiation.
 19. Process for preparing a dispersionof an insoluble organic compound comprising at least one group thatabsorbs UV radiation, which consists in subjecting particles of the saidorganic compound, suspended in a liquid medium, to a step of particlesize reduction until a mean particle size of between 10 nm and 5 μm isobtained, and in adding, before, during or after the step of particlesize reduction, at least one amphiphilic copolymer comprising at leastone hydrophilic block and at least one hydrophobic block.
 20. Processaccording to claim 19, characterized in that the step of particle sizereduction consists of a grinding operation in an aqueous medium. 21.Process according to claim 20, characterized in that the amphiphiliccopolymer comprising at least one hydrophilic block and at least onehydrophobic block is added before or during the grinding step. 22.Process according to one of claims 19 to 21, characterized in that theamphiphilic copolymer comprising at least one hydrophilic block and atleast one hydrophobic block is a nonionic polymer as defined in claims 4and
 5. 23. Process according to one of claims 19 to 22, characterized inthat the insoluble organic compound comprising at least one group thatabsorbs UV radiation is chosen from insoluble UV screening agents ofoxalanilide, triazine, benzotriazole, vinylamide, cinnamide, benzazole,benzofuran, arylvinylidene ketone, acrylonitrile amide, acrylonitrilesulphonamide, acrylonitrile carbamate or phenylenebis(benzoxazinone)type.
 24. Process according to claim 23, characterized in that theinsoluble UV screening agents are chosen from those described in claims7 to
 16. 25. Process according to one of claims 19 to 24, characterizedin that the particles of insoluble organic compound comprising at leastone group that screens out UV radiation represent from 5% to 70% byweight and preferably from 30% to 50% by weight of the final dispersion.26. Process according to one of claims 19 to 25, characterized in thatthe amphiphilic copolymer comprising at least one hydrophilic block andat least one hydrophobic block is added in a proportion of from 1 to 10mg and preferably in a proportion of from 1 to 5 mg per m² of surfacearea of particles of insoluble organic compound comprising at least onegroup that screens out UV radiation, after size reduction. 27.Dispersion comprising, in a liquid medium, (a) at least one insolubleorganic compound comprising at least one group that screens out UVradiation, in the form of particles with a mean size of between 10 nmand 5 μm, and (b) as dispersant, at least one amphiphilic copolymercomprising at least one hydrophilic block and at least one hydrophobicblock, chosen from the group formed by polyalkoxylated aliphaticalcohols of formula:H_(2n+1)C_(n)(CH₂CH₂O)_(x)(CH₂CH(CH₃)O)_(y)(CH(CH₃)CH₂O)_(z)H in which nis an integer between 5 and 20 and preferably between 7 and 19, x is aninteger between 2 and 20 and preferably between 4 and 10, y is aninteger between 2 and 20 and preferably between 4 and 10, the sum of y+zbeing an integer between 2 and 20 and preferably between 2 and 12;triblock copolymers of ethylene oxide and of propylene oxide, of formulaHO(CH₂CH₂O)_(a)(CH₂CH(CH₃)O)_(b)(CH₂CH₂O)_(c)H  in which a represents aninteger between 2 and 150, b represents an integer between 10 and 80 andc represents an integer between 2 and 150; products of condensation ofblock copolymers of ethylene oxide and of propylene oxide withethylenediamine, corresponding to the formula:

block copolymers of styrene and of ethylene oxide, polyethoxylatedpolyolefin succinates, and in particular the polyethoxylatedpolyisobutylene succinate of formula

in which PIB represents a polyisobutylene chain, n represents an integerbetween 2 and 15 and preferably between 7 and 10, and m represents aninteger between 2 and 15 and preferably between 2 and 6; blockterpolymers of (meth)acrylic acid, of a C₁₀₋₃₀ alkyl (meth)acrylate andof polyethylene glycol (meth)acrylate.
 28. Dispersion according to claim27, characterized in that it contains from 5% to 70% by weight andpreferably from 30% to 50% by weight of particles of insoluble organiccompound comprising at least one group that screens out UV radiation.29. Dispersion according to claim 27 or 28, characterized in that itcontains from 1 to 10 mg and preferably from 1 to 5 mg, per m² ofsurface area of particles of insoluble organic compound comprising atleast one group that absorbs UV radiation, of a dispersant. 30.Dispersion according to any one of claims 27 to 29, characterized inthat the liquid medium is an aqueous medium.
 31. Dispersion according toany one of claims 27 to 30, characterized in that the amphiphiliccopolymer comprising at least one hydrophilic block and at least onehydrophobic block is a nonionic polymer.
 32. Dispersion according to anyone of claims 27 to 31, characterized in that the insoluble organiccompounds comprising at least one group that absorbs UV radiation arechosen from insoluble UV screening agents of oxalanilide, triazine,benzotriazole, vinylamide, cinnamide, benzazole, benzofuran,arylvinylidene ketone, acrylonitrile amide, acrylonitrile sulphonamide,acrylonitrile carbamate and phenylenebis(benzoxazinone) type. 33.Dispersion according to claim 32, characterized in that the insoluble UVscreening agents of oxalanilide type are chosen from those of formula

in which T₁, T₁′, T₂ and T₂′ each independently represent a C₁₋₈ alkylradical or a C₁₋₈ alkoxy radical.
 34. Dispersion according to claim 32,characterized in that the insoluble UV screening agents of triazine typeare chosen from those of formula

in which R₁, R₂ and R₃ each independently represent a phenyl, phenoxy orpyrrolo group that is unsubstituted, or each independently bear one, twoor three substituents chosen from —OH, C₁₋₁₈ alkyl, C₁₋₁₈ alkoxy,carboxy(C₁₋₁₈ alkyl), C₅-C₈ cycloalkyl, methylbenzylidenecamphor,—(CH═CR′)_(n)(CO)—OR₄ in which R′ represents a hydrogen atom, a cyanogroup or a group COOR₄, with R₄=C₁₋₁₈ alkyl or cinnamyl, and n is 0or
 1. 35. Dispersion according to claim 32, characterized in that theinsoluble UV screening agents of benzotriazole type are chosen fromthose of formula

in which R₅ denotes a hydrogen atom or a C₁₋₁₈ alkyl radical, R₆ and R₇,which may be identical or different, denote a C₁₋₁₈ alkyl radicaloptionally substituted with a phenyl group, or of formula

in which R₈ and R₉, which may be identical or different, each representa C₁₋₁₈ alkyl radical that may be substituted with one or more radicalschosen from C₁₋₄ alkyl, C₅₋₁₂ cycloalkyl or aryl.
 36. Dispersionaccording to claim 32, characterized in that the insoluble UV screeningagents of vinylamide type are chosen from those of formulaT₃—(Y)_(r)—C(═O)—C(T₄)═C(T₅)—N(T₆)(T₇)  (V) in which T₃ is a C₁₋₁₈ andpreferably C₁₋₅ alkyl radical, or a phenyl group optionally substitutedwith one, two or three radicals chosen from OH, C₁₋₁₈ alkyl, C₁₋₈ alkoxyor —C(═O)—OT₈ in which T₈ represents a C₁₋₁₈ alkyl group; T₄, T₅, T₆ andT₇ each independently represent a C₁₋₁₈ and preferably C₁₋₁₅ alkylradical or a hydrogen atom; Y represents —NH— or an oxygen atom and r is0 or
 1. 37. Dispersion according to claim 32, characterized in that theinsoluble UV screening agents of cinnamide type are chosen from those offormula

in which R₁₀ represents a hydrogen atom or a C₁₋₄ alkyl group, R₁₁represents a hydrogen atom or a C₁₋₄ alkyl group, R₁₂ represents a group—(CONH)_(s)-phenyl in which s is 0 or 1 and the phenyl group may besubstituted with one, two or three groups chosen from OH, C₁₋₁₈ alkyl,C₁₋₈ alkoxy or —C(═O)—OR₁₃ in which R₁₃ is a C₁₋₁₈ alkyl, and morepreferably R₁₂ represents a phenyl, 4-methoxyphenyl orphenylaminocarbonyl group.
 38. Dispersion according to claim 32,characterized in that the insoluble screening agents of cinnamide typeare bis(α,β-disubstituted cinnamides) chosen from those of formula:

in which Ar₁ and Ar₂, which may be identical or different, eachrepresent a phenyl radical, an aromatic heterocycle, a group containinga fused phenyl nucleus or a group containing a fused aromaticheterocycle, and may bear one or more identical or differentsubstituents, B and D, which are other than a hydrogen atom, eachindependently represent an organic radical, A and C each independentlyrepresent an organic radical, and E represents a divalent organicradical, with the exclusion of the compounds for which Ar₁ and Ar₂ bothrepresent a phenyl group bearing a substituent —OR in which R representsa hydrogen atom or an organic radical, A and C both represent a cyanogroup, B and D both represent a C₁₋₃₅ alkyl or alkenyl group, and Erepresents a divalent organic radical.
 39. Dispersion according to claim32, characterized in that the insoluble UV screening agents of benzazoleor benzofuran type are chosen from those of formula

in which each of the symbols Y independently represents an oxygen orsulphur atom or a group NR₁₅, each of the symbols Z independentlyrepresents a nitrogen atom or a CH group, each of the symbols R₁₄independently represents an OH group, a halogen atom, a linear orbranched C₁₋₈ alkyl group optionally containing a silicon atom, or alinear or branched C₁₋₈ alkoxy group, each of the numbers m isindependently 0, 1 or 2, n represents an integer between 1 and 4inclusive, p is equal to 0 or 1, each of the numbers q is independentlyequal to 0 or 1, each of the symbols R₁₅ independently represents ahydrogen atom, a benzyl group or a linear or branched C₁₋₈ alkyl groupoptionally containing a silicon atom, A represents a radical of valencyn chosen from those of formulae:

in which each of the symbols R₁₆ independently represents a halogen atomor a linear or branched C₁₋₄ alkyl or alkoxy group, or hydroxyl, R₁₇represents a hydrogen atom or a linear or branched C₁₋₄ alkyl group,c=0-4, d=0-3, e=0 or 1 and f=0-2.
 40. Dispersion according to claim 32,characterized in that the insoluble screening agents of arylvinyleneketone type are chosen from those of formulae:

in which: n=1 or 2, A, in formula (XI) when n=1 or in formula (XII), isan aryl radical chosen from formulae (a) to (d) below, or in formula(XI) when n=2, is a radical chosen from formulae (e) to (h) below:

in which: each of the symbols R₄ independently represents an OH group, ahalogen atom, a linear or branched C₁₋₆ alkyl group optionallycontaining a silicon atom, a linear or branched C₁₋₆ alkoxy groupoptionally containing a silicon atom, a linear or branched C₁₋₅alkoxycarbonyl group, or a linear or branched C₁₋₆ alkylsulphonamidegroup optionally containing a silicon atom or an amino acid function, prepresents an integer between 0 and 4 inclusive, q represents 0 or 1, R₁represents hydrogen or an OH group, R₂ represents hydrogen, a linear orbranched C₁₋₆ alkyl group optionally containing a silicon atom, a cyanogroup, a C₁₋₆ alkylsulphonyl group or a phenylsulphonyl group, R₃represents a linear or branched C₁₋₆ alkyl group optionally containing asilicon atom or a phenyl group that can form a bicycle and optionallysubstituted with one or two radicals R₄, or R₂ and R₃ together form amonocyclic, bicyclic or tricyclic C₂₋₁₀ hydrocarbon-based residue,optionally interrupted with one or more nitrogen, sulphur and oxygenatoms and possibly containing another carbonyl, and optionallysubstituted with a linear or branched C₁-C₈ alkylsulphonamide group,optionally containing a silicon atom or an amino acid function; oncondition that when n=1, R₂ and R₃ do not form a camphor nucleus. 41.Dispersion according to claim 32, characterized in that the insolublescreening agents of acrylonitrile amide, acrylonitrile sulphonamide andacrylonitrile carbamate type are chosen from those of formula:

in which X₂ represents a divalent radical of formula —(C═O)—R′₃—(C═O)—,—SO₂—R″₃—SO₂— or —(C═O)—O—R″₃—O—(C═O)—, Y represents a radical —(C═O)—R₄or —SO₂R₅, R₂ represents a linear or branched C₁₋₈ alkyl group, n is 0,1 or 2, R′₃ represents a single bond or R″₃, R″₃ represents a linear orbranched C₁₋₃₀ divalent alkylene radical or a linear or branched C₃₋₃₀divalent alkenylene radical, which may bear one or more hydroxylsubstituents and which may contain, in the carbon-based chain, one ormore hetero atoms chosen from oxygen, nitrogen and silicon atoms, R₄represents a radical —OR₆ or —NHR₆, R₅ represents a linear or branchedC₁₋₃₀ alkyl radical or a phenyl nucleus that may be substituted withC₁₋₄ alkyl or alkoxy radicals, R₆ represents a linear or branched C₁₋₃₀alkyl or C₃₋₃₀ alkenyl radical, which may bear one or more hydroxylsubstituents and which may contain, in the carbon-based chain, one ormore hetero atoms chosen from oxygen, nitrogen and silicon atoms. 42.Dispersion according to claim 32, characterized in that the insolubleorganic screening agents of phenylenebis(benzoxazinone) type are chosenfrom those of formula:

in which R represents a divalent aromatic residue chosen from theformulae (e) to (h) below:

in which: each of the symbols R₄ independently represents an OH group, ahalogen atom, a linear or branched C₁₋₆ alkyl group optionallycontaining a silicon atom, a linear or branched C₁₋₆ alkoxy groupoptionally containing a silicon atom, a linear or branched C₁₋₅alkoxycarbonyl group, or a linear or branched C₁₋₆ alkylsulphonamidegroup optionally containing a silicon atom or an amino acid function, prepresents an integer between 0 and 4 inclusive, q represents 0 or 1.43. Dispersion according to any one of claims 27 to 42, characterized inthat the mean particle size of the insoluble organic compound comprisingat least one group that absorbs UV radiation is between 10 nm and 2 μm,preferably between 20 nm and 1.5 μm and in particular between 30 nm and1.0 μm.
 44. Cosmetic composition for topical use, in particular forphotoprotecting the skin and/or the hair, containing, in a cosmeticallyacceptable medium, (a) at least one insoluble organic compoundcomprising at least one group that screens out UV radiation, in the formof particles with a mean size of between 10 nm and 5 μm, and (b) atleast one dispersant chosen from amphiphilic copolymers comprising atleast one hydrophilic block and at least one hydrophobic block, preparedby dilution of a dispersion according to any one of claims 27 to 43, ina cosmetically acceptable medium.
 45. Composition according to claim 44,characterized in that it contains from 0.1% to 15% by weight andpreferably from 0.2% to 10% by weight of particles of insoluble organiccompound comprising at least one group that screens out UV radiation.46. Composition according to claim 44 or 45, characterized in that italso contains one or more water-soluble or liposoluble organicsunscreens that are active in the UV-A and/or UV-B range.
 47. Cosmeticcomposition according to one of claims 44 to 46, characterized in thatthe soluble organic sunscreens are chosen from the following: ethylhexylsalicylate, butyl methoxydibenzoylmethane, ethylhexyl methoxycinnamate,octocrylene, phenylbenzimidazole sulphonic acid, terephthalylidenedicamphor sulphonic acid, benzophenone-3, benzophenone-4,benzophenone-5, 4-methylbenzylidenecamphor, benzimidazilate,anisotriazine, ethylhexyl triazone, diethylhexyl butamido triazone,methylene bisbenzotriazolyl tetramethylbutylphenol, drometrizoletrisiloxane, and mixtures thereof.
 48. Cosmetic composition according toone of claims 44 to 47, characterized in that it also contains one ormore mineral pigments.
 49. Cosmetic composition according to claim 48,characterized in that the mineral pigments are chosen from nanopigmentsof metal oxides such as titanium oxide, iron oxide, zinc oxide,zirconium oxide and cerium oxide, which are optionally coated, andmixtures thereof.
 50. Cosmetic composition according to claim 49,characterized in that the nanopigments have a mean particle size ofbetween 5 nm and 100 nm and preferably between 10 nm and 50 nm. 51.Cosmetic composition according to one of claims 44 to 50, characterizedin that it also contains at least one agent for artificially tanningand/or browning the skin.
 52. Cosmetic composition according to any oneof claims 44 to 51, characterized in that it also contains one or moreformulation adjuvants chosen from fatty substances, physiologicallyacceptable organic solvents, thickeners, antioxidants, opacifiers,stabilizers, antifoams, fragrances, preserving agents, fillers,sequestering agents, propellants, pH modifiers and colorants, andmixtures thereof.
 53. Cosmetic composition according to any one ofclaims 44 to 52, characterized in that it also contains one or morecosmetic active principles chosen from vitamins, softeners, hydroxyacids, moisturizers, emollients, free-radical scavengers, substance pantagonists and anti-inflammatory agents, and mixtures of thesecompounds.
 54. Cosmetic composition according to any one of claims 44 to53, characterized in that it constitutes a cosmetic composition forprotecting the skin or the hair, an antisun composition or a makeupproduct.